1. Field of the Invention
The present invention relates to a continuous flow type homogenizer which is adapted for disrupting the cell membrane of a cell to isolate subcellular organelles, etc., included in the cell.
2. Description of the Prior Art
There is a necessity in biological, medical, and other research fields to isolate enzymes and subcellular organelles such as Golgi apparatus and mitochondria included in cells. For the isolation, the cells shall be disrupted by some disrupting means. There are several prior art means for disrupting cell membranes (the means hereinafter called the "homogenizer"), in which one utilizes ultrasonic waves, another applying nitrogen gas, etc., with high pressure and removing the pressure abruptly to disrupt the cell membranes, or the other applying pressure by hydraulic machine on cells in liquid to pass the cells through small holes to disrupt the cell membranes. There is a further prior art method which is called the potter type in which a pestle is rotated in a tubular container (hereinafter called the "cylinder") by an exclusive rotary driving unit while the cylinder is manually reciprocated up and down to disrupt the cell membranes. The pestle may be rotated in the cylinder by utilizing an existing rotary machine.
Generally, such prior art homogenizers are not efficient in disrupting cells and inconvenient in handling. For instance, a cylinder of the potter type homogenizer which is widely used shall manually be moved up and down. That reduces the efficiency of device. In other devices which use ultrasonic waves or high pressure nitrogen gas, their sizes become large, and that pushes their costs up.
In the case which uses a stirrer or an existing rotary machine to rotate a pestle, it is difficult to control the rotational speed of pestle according to the service conditions of the homogenizer, such as the nature of tissue to be homogenized. Further, the characteristic of rotational speed change of existing rotary machine, etc., is not suitable for the homogenizer. It is preferable for the homogenizer to change its speed continuously and gently with a constant velocity gradient when starting and stopping the homogenizer or during the change of its speed.
If the homogenizer is not properly rotated, or if a clearance between the pestle and cylinder is not set properly, the homogenizing operation will not properly be carried out, and undesirable friction heat may be caused to deteriorate the homogenized tissue.
Supposing tissue to be homogenized are A and B, the temperature of tissue A before the homogenization T.sub.A .degree. C., the temperature of tissue B before the homogenization T.sub.B .degree. C., diameter of cylinder D.sub.S mm, the material of cylinder is glass, the diameter of pestle D mm, the material of pestle is fluororesin, the linear expansion coefficient of glass at reference temperature of 20.degree. C. "L.sub.G " (3.times.10.sup.-6 to 20.times.10.sup.-6 /.degree. C.), and the linear expansion coefficient of fluororesin "L.sub.F " (about 10.times.10.sup.-5 /.degree. C.). The change .DELTA.d of clearance "d" is approximately given by the following equation: EQU .DELTA.d=D.sub.S.L.sub.G (T.sub.A -20)-D.sub.p.L.sub.F (T.sub.B -20) .div.-D.sub.p.L.sub.F (T.sub.B -20)
Namely, the .DELTA.d varies according to the linear expansion of pestle. The value of .DELTA.d at, for instance, 30.degree. C. with the pestle diameter of 20 mm, reaches 0.03 mm. In other words, if there is a temperature difference of 30.degree. C. between the tissue A and B to be homogenized, there is caused a difference of 0.03 mm in the clearance "d". Since the homogenizing operation shall be performed with the clearance being kept at 0.15 to 0.20 mm as mentioned in the above, the change of clearance in the value of 0.03 mm may effect largely on the homogenizing operation.
Other factors which will degrade the quality of homogenized tissue are the operator's erroneous observation of the operation due to the lowered transparency of container, and impurities entering from the upper opening of container.
Among potter type homogenizers described in the above, there is a kind which is covered (coated) with the polyvinyl chloride (PVC). The cover (coating) is provided to protect an operator from injuring his hands with the broken pieces of cylinder, if the cylinder is broken during the operation.
However, the cover according to prior art is formed only by coating the cylinder with thin plastics so that broken pieces may happen to break through the coating film. Further, it is difficult to observe the homogenizing condition if the transparency of the coating film is deteriorated. The transparency of the coating film is deteriorated not only when external surface thereof is damaged, but also when water enters between the cylinder and the coating film while the cylinder is being washed, or when water and air enter through pinholes that may be on the coating film. If the coating film is thickened to improve its strength, it is unavoidable that the transparency of coating film is deteriorated preventing the observation of homogenizing condition when the external surface of plastic coating film is damaged or when water enters between the cylinder and the coating film while the cylinder being washed.